International Patent Number WO94/20809 relates to firearms of the type described. Field tests of prototype versions of firearms utilizing barrels of the type described have shown that such barrel assemblies perform to expectations. However the inventor has proposed useful variations, including munitions, as well as improvements which may assist in either the efficient production of such firearms or facilitate their performance or useability. Furthermore the inventor envisages that single barrel rates of fire in excess of 40,000 rounds/minute may be achievable in practice and this possibility creates further scope for munitions of conventional style and firearms utilizing barrels of the type described.